Tip for a marking instrument



Patented Feb. 18, 1941 PATENT OFFICE 2,232,231 'rrr Fon A MARKING'INSTRUMENT OCal Hanson, Chicago, Ill., assignor to W. A. Shealer PenCompany, Fortl Madison, Iowa, a corporation of Delaware ApplicationJanuary 31, 1940,1ser'ia1N0. 316,506

6 Claims.v

This invention relates to a tip for a marking instrument and has specialreference to 'a shell for the writing point end of a mechanical pencilor the like, the shell having an axial opening therethrough of adiameter to permit the passage of a lead or other marking medium.

More particularly, this inventionrelates to a tip for a markinginstrument comprising a rigid shell having an end opening through whichthe marking medium extends, the material of the shell having a portionof reduced thickness adjacent the end opening thereof to present aminimized clearance between the side wall ofthe marking medium and aguide or the like against which the shell may be rested.

'I'he present invention contemplates a tip for mechanical pencils of theusual type on the market todayfwhereby such a pencil may be employed bydraftsmen, engineers, and lthe like, where it is necessary, for example,toguide the pencil with a straight edge in producing a line. The usualtip for mechanical pencils or other marking instruments is formed of arelatively soft base metal sometimes plated with a precious metal. Mostmetals thus employed are of a comparatively great thickness since asubstantial strength is required in supporting the lead or markingmedium projecting therethrough and in opposing stresses such as areoccasioned by dropping the marking instrumen-t on a hard surface.

In the use of such a usual marking instrument with a guide or straightedge there is a very substantial clearance between the side wall of themarking medium and the guide if the tip is rested against the guide or,should the lead be rested against the guide directly, then a verysubstantial portion of the lead is extended from the end of the pencil.In the first instance where the thickness of the wall of the tip spacesthe lead substantially from the guide, the mark produce-d is either notaccurate or very diflicult to make accurate and, in the latter instance,where the pencil lead is extended sufficiently beyond the tip of thewriting instrument so as to contact the guide of itself, the lead isweakened by reason of not having a proper support therefor and is veryreadily broken.

In the usual tip construction it is impractical to extend the leadsuiliciently for the purpose of sharpening to produce a line line as isnecessitated in drafting. 'Ihe sharpened point needs extend such asubstantial distance beyond the end of the tip that it will not functionsatisfactorily without breaking. The present invention contemplates theprovision of a tip in which the thickness of the side wall thereof isreduced to such an extent that accurate workmanship may be obtained by adraftsman in resting the tip directly against the guide. Also the tipmay be provided with a side wall opening or opposed side wall openingsformed by gradually reducing the thickness of the side wall resulting insuch opening or openings in communication with the end opening. Such aconstruction presents exposed Wall portions of the marking mediuminwardly of the end of the shell so lthat the marking medium may besharpened inwardly beyond its supported portion to have an extendingpointed end portion of comparatively small length.

With a construction as above identied a minimized clearance between theside wall of the marking medium and a guide against which the tip mayrest is provided and Where side wall openings communicate with the endopening, exposed wall portions of the marking medium inwardly of the endof the shell provide that the marking medium may be pointed inwardly ofthe end of the shell and thus reduce to a minimum the amount of markingmedium which extends beyond the end of the shell.

One of the objects of this invention is to provide a tip for a markinginstrument of the character indicated above whereby the clearancebetween the side wall of the marking medium and the guide against whichthe tip may rest is' substantially minimized.

Another object of this invention is to provide a tip for a markinginstrument of the type hereinabove mentioned in which exposed wallportions of the marking medium are presented inwardly of the end of theshell so that the marking mediummay be sharpened with a minimum lengthof the marking medium extending from the end of the tip.

Other objects and advantages of this invention will hereinafter be moreparticularly pointed out and, for a more complete understanding of thecharacteristic features of this invention, reference may now be had tothe following description when taken together with the accompanyingdrawing, in which latter:

Figure 1 is a front elevational view of a mechanical pen-cil having atip at the writing point end thereofl incorporating the features of thisinvention;

Fig. 2 is an enlarged side elevational view of a fragmentary portion ofthe end of the-mechanical pencil shown in Fig. 1;

Fig. 3 is an enlarged fragmentary View of the lower end of themechanical pencil of Fig. 1;

Fig. 4 is a view similar to Fig. 2 showing a portion of the tip insection;

Fig. 5 is a view similar to Fig. 3 showing a portion of 4the tip insection; and

Fig. 6 is an enlarged perspective view of the tip shown in the precedinggures.

Referring now more particularly to the drawing, the tip embodying thefeatures of the present invention is shown attached to the writing pointend of a mechanical pencil I0, the pencil being of a standardconstruction. The tip comprises a conical-shaped shell I I of any rigidmaterial.

The shell II is formed by swaging a piece of tubular stock or it may beprocessed on a screw machine from rod stock. The material of the shellII is ordinarily of a base material such as brass having a nickel orprecious metal plating thereon. In the present construction, while theabove material may be employed it has been found preferable to employstainless steel having a high chromium content, the shell thus formedbeing of substantially less thickness than that of brass or suchmaterial and yet having the same strength. In practice it has been foundthat the tip may be swaged from a .005" wall stainless steel tube.

Referring more particularly to Fig. 4, it will be noted that the taperedoutside wall of the conical shell II is straight and that the insidewall thereof is likewise straight to the end opening I2 which is ofuniform diameter throughout its length. After the shell II has beenswaged into conical shape, a .037" hard steel wire is inserted in theend of the swaging mandrel and extends through the end opening of theshell with the tip being formed down on the steel wire to produce theopening I2 of uniform diameter. 'I'he thickness of the material at theextreme end of the shell indicated by the numeral A is .0055" thuspresenting a minimized clearance between the side wall of the markingmedium extending through the opening I2 and any guide against which theshell II may rest.

In perhaps most conditions of use this clearance is sufliciently smallto effect a high degree of accuracy, yet it is a further object of thisinvention to present exposed wall portions of the marking mediuminwardly of the end of the shell in order that the marking medium may beexposed for purposes of sharpening to a very iine point and further thatthe sharpened point need only extend a comparatively short distance fromthe end of the shell. In order to accomplish this result, opposed sidesof the shell are ground to present ilattened portions I3, the flattenedportions extending at a greater angle than the normal inclination of theconical surface of the shell. This results in gradually reducing theshell in thickness as shown more particularly in Figs. 3 and 5. In Fig.3, the normal contour of the shell is shown in dot-dash lines with theactual contour of the shell after grinding being shown in full lines.The marking medium I4 is shown in its normal size in dotted lines and inits actual shape after sharpening in full lines.

In use with a guide, either the marking medium or the shell may beengaged against the guide. In both instances an accurate marking on asurface is obtained in conformity with the guide. In the usual markinginstrument, accuracy is obtained strictly in accordance with manualmanipulation, depending for example on maintaining the same angularityof the instrument in the movement thereof along the guide.

While but a single embodiment of this invention is herein shown anddescribed, it is to be understood that Various modifications thereof maybe apparent to those skilled in the art Without departing from thespirit and scope of this invention and, therefore, the same is only tobe limited by the scope of the prior art and the appended claims.

I claim:

1. A tip for a marking instrument comprising a rigid conical shellhaving an end opening through which the marking medium extends, thematerial of said shell having opposed portions of gradually reducingthickness in the direction of and terminating adjacent the end openingthereof to present opposed flattened side walls for producing aminimized clearance between the side wall of the marl-ring medium and aguide against which said shell may rest.

2. A tip for a marking instrument comprising a rigid conical shellhaving an end opening through which the marking medium extends,.thematerial of said shell having opposed portions of gradually reducingthickness in the direction. of and terminating adjacent the end openingthereof to present opposed attened side walls terminating in side wallopenings to expose portions of the side wall of the marking medium.

3. A tip for a marking instrument comprising a conical metallic shellhaving an opening at the 4smaller end thereof through which the markingmedium extends, the material of said shell at opposed portions thereofbeing gradually reduced in thickness to terminate in a side wall openingto present exposed wallportions of said marking medium inwardly of theend of said shell.

4. A tip for a marking instrument comprising a conical metallic shellhaving an opening at the smaller'end thereof through which the markingmedium extends, said shell having opposed paraboloid-shaped openings atthe smaller end thereof to present exposed wall portions of said markingmedium inwardly of the end of said shell.

5. A tip for a marking instrument comprising a conical metallic shellhaving an opening at the smaller end thereof through which the markingmedium extends, the material of said shell at opposed portions thereofbeing gradually reduced in thickness toward said end opening terminatingin a side wall opening to present .exposed wall portions of said markingmedium inwardly of the end of said shell.V

6. A tip for a marking instrument comprising aA conical metallic shellhaving an'opening at the smaller end thereof through which the markingmedium extends, the material of said shell at opposed portions thereofbeing gradually reduced in thickness toward said end opening to presentopposed flattenedsidewalls terminating in paraboloid-shaped openings incommunication with said end opening for exposing-wall portions of saidmarking medium inwardly of the end of said shell. l

OCAL HANSON.

